PART V. 



NON-MARINE MOLLUSCA OF PATAGONIA. 



BY 



HENRY A. PILSBRY, 

 Academy of Natural Sciences, Philadelphia. 



This report deals with the non-marine mollusks of Tierra del Fuego 

 and Patagonia as far north as the thirty-ninth parallel, where the Rio 

 Negro Valley forms a transition region, the Patagonian fauna giving place 

 to the La Platan. 



The scope of the work has been extended to include some account of 

 all the South American forms of certain little-known families, such as the 

 Amnicolidcc and Sphariidce, and all of the Chilinidce occurring east of the 

 Andes. Finally, the relationships of the South American molluscan fauna 

 with the faunas of other continents are considered. 



The collections made by Mr. J. B. Hatcher and placed in my hands by 

 Professor William B. Scott form the basis of this report. The material 

 from the region along the Rio Chico de la Santa Cruz and in the base of 

 the Andes above its head is ample. Elsewhere but few mollusks were 

 collected, and I have used material which I owe to the generosity of Dr. 

 H. von Ihering, Director of the Museu Paulista, Dr. W. H. Rush, U.S.N., 

 and others. 



Zonal Distribution of Patagonian Mollusca. 



An inspection of the data existing on Patagonian mollusks shows that 

 several faunulas largely distinct in species occupy zones extending from 

 the Atlantic to the Andes and succeeding one another from north to south. 

 So far as aquatic animals are concerned, these zones are determined by 

 the drainage systems, which are separated by poorly watered plains, and 

 flow independently into the Atlantic. The aquatic mollusks known from 

 these several zones are enumerated below. 



Chilina, Lymiicsa and Pisidiitni are the only genera of fresh-water mol- 

 lusks which extend throughout Patagonia, the first two also in Tierra del 



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